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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 12 May 2018 by John Hartz

A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week.

Editor's Pick

Methane, Climate Change, and Our Uncertain Future

Methane is generally considered secondary to carbon dioxide in its importance to climate change, but what role might methane play in the future if global temperatures continue to rise?

Flooded permafrost tundra in northeast Siberia. Hydrology is a key control on methane emissions in wetland and permafrost ecosystems. Credit: Joshua Dean

The greenhouse gas, methane, is produced by both natural processes and human activities. While there has been much attention paid to curbing anthropogenic emissions, a changing climate will likely increase the production of natural methane. In an open access article recently published in Reviews of Geophysics, Dean et al. [2018] describe the ways in which biological, geochemical, and physical systems influence methane concentrations and explore how methane levels in natural systems may alter in a warming climate. Here the authors answer some questions about the sources and significance of methane, and indicate some future research directions.

Comments

In their 2011 Paper, Schuur and Abbott concluded that no more than 2.7% of greenhouse gasses emitted by melting of permafrost would be in the form of CH4, with 93.3% of CH4 being oxidised and emitted as CO2. This widely accepted view ignored the fact that when the top 2-3 metres of permafrost degrades, much of the land is covered in water due to poor drainage. This inhibits oxidation of CH4 since methanotrophic bacteria responsible for this process cannot function in anoxic conditions normally found in waterlogged land.

It should be expected that CH4 emissions from permafrost degredation, both onshore and from the submerged continental shelf bordering the Arctic Ocean, will therefore be very much higher and its oxidation in the atmosphere very much slower due to depletion of hydroxil (H1O) radicals essential for this process. Hydroxil radicals are derived from ozone and their depletion is due in part to anthropogenic effects on the zone layer and on CH4 emissions exceeding the rate of hydroxil formation.

The likely outcome is that global warming will produce significantly increasing CH4 emissions beyond human control (unlike farming and industrial emissions) and well beyond the capacity of hyroxils to oxidise. The result will be that the lifespan of CH4 in the atmosphere, now 10-12 years, will increase – as will its contribution to global warming, further degrading permafrost and releasing even greater quantities of CH4 to the atmosphere. CH4 emissions from permafrost will become an increasingly serious problem.

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